A double-blind placebo-controlled study of the effectiveness and tolerability of oral stevioside in human hypertension.
AIMS: Stevioside is a natural plant glycoside isolated from the plant Stevia rebaudiana which has been commercialized as a sweetener in Japan for more than 20 years. Previous animal studies have shown that stevioside has an antihypertensive effect. This study was to designed to evaluate the effect of stevioside in human hypertension. METHODS: A multicentre, randomized, double-blind, placebo-controlled study was undertaken. This study group consisted of 106 Chinese hypertensive subjects with diastolic blood pressure between 95 and 110 mmHg and ages ranging from 28 to 75 years with 60 subjects (men 34, women 26; mean +/- s.d., 54.1+/-3.8 years) allocated to active treatment and 46 (men 19, women 27; mean +/- s.d., 53.7+/-4.1 years) to placebo treatment. Each subject was given capsules containing stevioside (250 mg) or placebo thrice daily and followed-up at monthly intervals for 1 year. RESULTS: After 3 months, the systolic and diastolic blood pressure of the stevioside group decreased significantly (systolic: 166.0+/-9.4-152.6+/-6.8 mmHg; diastolic: 104.7 +/- 5.2-90.3+/-3.6 mmHg, P<0.05), and the effect persisted during the whole year. Blood biochemistry parameters including lipid and glucose showed no significant changes. No significant adverse effect was observed and quality of life assessment showed no deterioration. CONCLUSIONS: This study shows that oral stevioside is a well tolerated and effective modality that may be considered as an alternative or supplementary therapy for patients with hypertension. (+info)
Inhibition of the nuclear factor kappa B (NF-kappa B) pathway by tetracyclic kaurene diterpenes in macrophages. Specific effects on NF-kappa B-inducing kinase activity and on the coordinate activation of ERK and p38 MAPK.
The anti-inflammatory action of most terpenes has been explained in terms of the inhibition of nuclear factor kappaB (NF-kappaB) activity. Ent-kaurene diterpenes are intermediates of the synthesis of gibberellins and inhibit the expression of NO synthase-2 and the release of tumor necrosis factor-alpha in J774 macrophages challenged with lipopolysaccharide. These diterpenes inhibit NF-kappaB and IkappaB kinase (IKK) activation in vivo but failed to affect in vitro the function of NF-kappaB, the phosphorylation and targeting of IkappaBalpha, and the activity of IKK-2. Transient expression of NF-kappaB-inducing kinase (NIK) activated the IKK complex and NF-kappaB, a process that was inhibited by kaurenes, indicating that the inhibition of NIK was one of the targets of these diterpenes. These results show that kaurenes impair the inflammatory signaling by inhibiting NIK, a member of the MAPK kinase superfamily that interacts with tumor necrosis factor receptor-associated factors, and mediate the activation of NF-kappaB by these receptors. Moreover, kaurenes delayed the phosphorylation of p38, ERK1, and ERK2 MAPKs, but not that of JNK, in response to lipopolysaccharide treatment of J774 cells. The absence of a coordinate activation of MAPK and IKK might contribute to a deficient activation of NF-kappaB that is involved in the anti-inflammatory activity of these molecules. (+info)
Effect of steviol on para-aminohippurate transport by isolated perfused rabbit renal proximal tubule.
An inhibitory effect of steviol, metabolite of the natural sweetener stevioside, on transepithelial transport of p-aminohippurate (J(PAH)) was observed in isolated S(2) segments of rabbit renal proximal tubules using in vitro microperfusion. Addition of steviol (0.01--0.25 mM) to the bathing medium significantly depressed J(PAH) (approximately 50--90%). This inhibitory effect was dose-dependent and was maximum at a concentration of 0.05 mM. To further examine this effect, a steviol concentration (0.01 mM) that produced approximately 50% inhibition of J(PAH), was chosen. Addition of 0.01 mM steviol to the bathing medium significantly depressed J(PAH) by about 50 to 60%. Steviol at the same concentration (0.01 mM), when present in the tubule lumen, had no significant effect on J(PAH). Addition of 0.01 mM steviol to lumen and bath simultaneously, produced a slightly greater inhibitory effect compared with addition to bath alone (60 versus 70%). A higher concentration of steviol, 0.05 mM (which maximally inhibited J(PAH) when on the basolateral side), was required on the luminal side than on the basolateral side before an inhibitory effect was observed. To further examine the mechanism by which steviol inhibited J(PAH), its effect on Na(+)-K(+) ATPase activity and ATP content was determined. Steviol at concentrations of 0.01 and 0.05 mM had no effect on Na(+)-K(+) ATPase activity or cell ATP content. Kinetic analyses indicated that steviol can competitively inhibit PAH transport at the basolateral membrane. The present study clearly showed that steviol can have a direct inhibitory effect on renal tubular transport by competitive binding with organic anion transporter. (+info)
Mutagenicity of steviol and its oxidative derivatives in Salmonella typhimurium TM677.
Stevioside is natural non-caloric sweetner isolated from Stevia rebaudiana BERTONI, which has been used as a non-caloric sugar substitute in Japan. Pezzuto et al. demonstrated that steviol shows a dose-dependent positive response in forward mutation assay using Salmonella typhimurium TM677 in the presence of metabolic activation system (Aroclor induced rat liver S9 fraction). Our studies were carried out to identify the genuine mutagenic active substance from among the eight steviol derivatives. Steviol indicate almost similar levels of mutagenicity under the presence of S9 mixture, as reported by Pezzuto et al. 15-Oxo-steviol was found to be mutagenic at the one tenth the level of steviol itself under the presence of S9 mixture. Interestingly, specific mutagenicity of the lactone derivative under the presence of S9 mixture was ten times lower than that of the lactone derivative without the addition of S9 mixture. (+info)
The influence of mouthrinses with antimicrobial solutions on the inhibition of dental plaque and on the levels of mutans streptococci in children.
The effect of daily mouthrinses on dental plaque accumulation and on salivary mutans streptococci was investigated in 200 children. The utilized solutions were: a placebo solution composed of mentholated deionized water (group I); 0.12% chlorhexidine gluconate associated to 0.05% sodium fluoride (group II); 0.2% chlorhexidine digluconate (group III), and 0.5% stevioside mixed with 0.05% sodium fluoride, with pH 3.4 (group IV). In order to verify the effect on plaque formation, the accumulation of plaque was assessed by means of the Loe12 index, at the beginning and at the end of the experiment, whereas the quantification of cariogenic streptococci was accomplished on three saliva samples collected at 3 different moments: before the first mouthrinse, 24 hours after the first mouthrinse and 1 week after the last mouthrinse. The mouthrinsing routine was carried out on a daily basis during 4 weeks. Five milliliters of solution were rinsed during 1 minute. The results revealed 4.10, 26.75, 41.20, and 5.91% of reduction in plaque accumulation for groups I, II, III, and IV, respectively. Comparisons between the groups as to plaque reduction revealed that groups II and III were significantly different from groups I (control) and IV (p < 0.05), but did not differ from each other. The solution utilized by group III was the least accepted by children and, as the solution utilized by group II, caused mild dental pigmentation. There were no statistically significant differences as to the levels of mutans streptococci, probably due to the low initial levels observed in each one of the four groups. (+info)
A new ent-kaurane diterpenoid glycoside from the leaves of Cussonia bojeri, a Malagasy endemic plant.
A new ent-kaurane diterpene glycoside, beta-D-glucopyranosyl 17-hydroxy-ent-kauran-19-oate-16-O-beta-D-glucopyranoside (4) was isolated from the dried leaves of Cussonia bojeri SEEM., together with four known compounds identified as 16beta,17-dihydroxy-kauran-19-oic acid (1), beta-D-glucopyranosyl 16beta,17-dihydroxy-(-)-kauran-19-oate (2), paniculoside IV (3), and rutin (5). The structure of 4 was deduced on the basis of chemical and spectroscopic evidence. (+info)
Inhibitory effect of stevioside on tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin.
Four steviol (ent-kaurene-type diterpenoid) glycosides, stevioside, rebaudiosides A and C, and dulcoside A, have been isolated from Stevia rebaudiana BERTONI. These compounds showed strong inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice. The 50% inhibitory dose of these compounds for TPA-induced inflammation was 54.1-291.6 micro g/ear. Furthermore, at 1.0 and 0.1 mg/mouse of stevioside mixture, the mixture of these compounds markedly inhibited the promoting effect of TPA (1 micro g/mouse) on skin tumor formation initiated with 7,12-dimethylbenz[a]anthracene (50 micro g/mouse). (+info)
A novel ent-kaurane diterpenoid from the Croton tonkinensis GAGNEP.
A novel ent-kaurane diterpenoid, ent-1alpha-acetoxy-7beta,14alpha-dihydroxy-kaur-16-en-15-on has been isolated from leaves of Croton tonkinensis GAGNEP. Its structure was determined by a combination of spectroscopy, X-ray crystallographic analysis and the chemical reaction acetylation. (+info)